Insulation materials exhibit a broad range of raw material bases, from fibers to plastic foams, expanded resinous materials, bond hollow particles etc. Elastomeric or rubber based insulation (FEF, factory made elastomeric foam, e.g. according to EN 14304) is preferred among insulation materials, especially when it comes to insulate complex geometries and/or when talking about (at least partially) cold installations. This is due to its flexibility on the one hand and its in-built vapor barrier properties on the other hand. Its flexibility, however, is also one of its major drawbacks as is shown in more detail below.
Other materials exhibiting less flexibility, such as thermoplastic or resin foams, but also fiber based insulation, are not easy to be applied on round shaped installations due to their rigidity. They lead to gaps or air inclusions, which are undesirable due to poor energy efficiency, noise reduction and condensation prevention reasons. Condensed water may cause erosion of the structure. As such an insulation material itself is not or not sufficiently compressible, gaps are very likely already by production tolerances of the insulation mat itself, but also of the installation to be insulated, leading to some millimeters of deviation per centimeter of metal pipe diameter already (see e.g. EN 10216 and EN 13480).
However, tightly mounted insulation is required almost everywhere, but can, so far, only be provided by (properly) using flexible insulation (FEF). For smaller pipes such materials may be appropriate, but problems occur when it comes to larger installations: the flexible and, thus, soft material will sag when mounted horizontally and collapse when loaded with weight vertically. In any case the danger of losing the structural integrity of the insulation system is significant and may lead to poor energy efficiency, noise reduction and condensation prevention reasons. Applying strips or belts as supports is costly and does not provide sufficient safety.